1. Field of the Invention
The invention relates to a device for carrying out gas reactions, the device comprising a plasma reactor with a through-flow of gases, particularly a large-volume plasma reactor, which has a plasma chamber, particularly a cylindrical plasma chamber. The invention further relates to a method for carrying out gas reactions wherein a flow of gases or a flow of gasifiable substances is guided through a plasma, especially a plasma that is excited by microwaves.
2. Description of the Prior Art
Gases may flow through a device comprising a plasma reactor, particularly a cylindrical plasma reactor, to which microwaves are fed via coupling points, whereupon gas reactions may occur due to high excitation of the gases by the plasma. In particular, it is possible to carry out syntheses of substances and gas purifying reactions.
Known devices for the production of microwave plasmas consist of a plasma chamber, a microwave-feeding resonator with a microwave generator for producing the plasma, and coupling points, e.g. slots, antennas or the like, which are regularly arranged in the metal wall between the resonator and the plasma chamber for coupling the microwave into the plasma chamber.
Known plasma reactors for carrying out gas reactions use thermal plasma jets that require high powers of several times 10 kW and which heat the process gases to several times 1000 or even 10000 K. The power is introduced into small plasma volumes of several cubic centimeters (cm3) with power densities of several times 1000-10000 W/cm3.
According to DE 19 600 223, the resonator, in the form of a ring of rectangular cross-section, surrounds the metal wall with coupling points of the cylindrical, tubular plasma chamber.
Arrangements according to DE 19600223, for example, indeed produce non-equilibrium or non-thermal plasmas, in plasma chambers having a volume of several times 1000 cm3 and power densities of several W/cm3, at a microwave excitation frequency of 2.45 GHz, but they do not permit throughput of larger volume flows and corresponding gas velocities. The efficiency of such non-thermal plasmas, i.e. power input/turnover is markedly better as there is not as much energy wasted on the—generally useless—heating of the neutral gas.
Also suitable as microwave excitation frequency are, in particular, the commercially employed 915 MHz and 440 MHz, with correspondingly scaled plasma sources.
Known resonators that may be employed in accordance with the invention may also enclose a cylindrical wall of the plasma chamber with coupling points, either completely or as segments of a jacket having the same longitudinal axis, or they may be arranged within the cylindrical plasma chamber, e.g. in its axis. Due to the geometry of the resonator and the essentially tubular-cylindrical plasma chamber, and due to the regular arrangement of the coupling points between resonator and plasma chamber, certain wave patterns, so-called modes, are produced in the interior of the plasma chamber with optimal effectiveness of the plasma. The microwave generator may also be complemented or replaced by chemical, electromagnetic or high-frequency excitation.
Gases in the plasma chamber are excited by the plasma, whereby, inter alia, luminous effects are created. With the known reactors, it is of disadvantage that a gas flow disturbs the plasma even at low flow rates and pushes the plasma out of the chamber and causes the plasma to break down, which is thereby extinguished. It is not possible to achieve high gas throughputs and high gas flow velocities with the known reactors.
Known gas reactions and gas syntheses can also take place in the arc with discharge electrodes; here, the temperatures are too high for many purposes, the gas flow is impeded by the electrodes, and the high energy consumption is disadvantageous.